I find that the DOOM game plays in a screen that's too small for the game to be enjoyable, in X. If you want to play DOOM there's a good DOOM clone: FreeDOOM with more interesting weapons and monsters, and slightly better graphics. If you're a DOOM fan you should make a FAT32 partition and install FreeDOS to it, (include FreeDOOM in the setup process). That's the only proper way to play original DOOM these days.